This invention relates to a method for the die casting of articles, particularly items which are low in gas and oxides and which have a low porosity.
In the work entitled "Moderne Druckgussfertigung" ("Present-day Die Casting") by Ernst Brunhuber (published by Fachverlag Schiele und Schon GmbH, Berlin, Germany) there is described, on pages 57-60 a horizontally arranged cold-chamber die casting apparatus in which the molten material is drawn through a suction pipe by means of a vacuum.
The above process involves the disadvantage that, as the casting piston passes, during its forward stroke, over the suction opening, the metal admitted to the casting chamber is sheared off, whereby between the casting piston and the walls of the casting chamber metal residues appear which may not be entirely removed during the normal working cycle. These metal residues adversely affect an economical performance of the die casting process because they may lead to the jamming of the piston as well as to an increased wear of the piston and the casting chamber.
According to U.S. Pat. No. 3,009,218 the metal residues may be removed by shearing them off the casting piston by means of a sharp edge provided on a closure member of the casting chamber and collecting them in a receiving chamber provided in the closure member. It is a disadvantage of such an arrangement that the shearing off of the residues causes an impermissible wear of the casting piston.